Stabilization of a drogue body

ABSTRACT

A refueling drogue adapted to connect to a refueling hose extending from a refueling aircraft. The refueling drogue may include an active control system, wherein, in an exemplary embodiment, the active control system is adapted to regulate the position of the drogue to maintain a substantially fixed orientation relative to a refueling aircraft.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.10/697,564 filed on Oct. 31, 2003, which claims priority to U.S.Provisional Application Ser. No. 60/498,641 filed on Aug. 29, 2003. Thisapplication claims priority to both of these applications, andincorporates the contents of both of these applications by referenceherein in their entirety.

BACKGROUND OF THE INVENTION

Aerial refueling via the probe and drogue method is known. In anexemplary refueling scenario, a refueling drogue connected to arefueling hose is unreeled from a refueling aircraft towards a receiveraircraft (an aircraft to be refueled), such as a fighter plane. Thereceiver aircraft has a refueling probe extending from the aircraft. Thereceiver aircraft maneuvers to the refueling drogue and inserts itsrefueling probe into the refueling drogue, at which point the refuelingdrogue “locks” onto the refueling probe, and a transfer of fuel from therefueling aircraft to the receiver aircraft is conducted.

It is desirable that the drogue remain as stationary as possible and/orthat the drogue not rotate when extended from the refueling hose awayfrom the refueling aircraft towards the receiver aircraft, at leastbefore contact between the drogue and the probe is made. Unfortunately,the hose-drogue combination has a relatively large dynamic response todisturbances, so when the drogue is subjected to wind gusts and/orturbulence, the motion of the drogue becomes somewhat unpredictable, asforces imparted onto the drogue by the air cause the drogue to moveand/or rotate, thus making it difficult to position the refueling probeof the aircraft to be refueled into the refueling drogue.

Thus, there is a need to reduce the disturbance response of a refuelingdrogue that has been extended on a refueling hose so that the movementof the drogue resulting from wind/turbulence is substantially reduced toimprove the ease by which the refueling probe can be inserted in therefueling drogue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a first embodiment of the presentinvention.

FIG. 2 shows an implementation of an embodiment of the presentinvention.

FIG. 3 shows another embodiment of the present invention.

FIG. 4 shows yet another embodiment of the present invention.

FIG. 5 shows a detailed view of a component of the embodiment shown inFIG. 4.

FIG. 5 a shows a cross-sectional view of the component shown in FIG. 5.

FIG. 6 shows yet another embodiment of the present invention.

FIG. 7 shows yet another embodiment of the present invention.

FIG. 8 shows yet another embodiment of the present invention.

FIG. 9 shows yet another embodiment of the present invention.

FIG. 10 shows yet another embodiment of the present invention.

FIG. 11 shows yet another embodiment of the present invention.

FIG. 12 shows yet another embodiment of the present invention.

FIG. 13 shows the orientation of the axis of the refueling hose withrespect to the velocity vector of the airstream as seen from onereference point.

FIG. 14 shows the orientation of the axis of the refueling hose withrespect to the velocity vector of the airstream as seen from anotherreference point.

FIG. 15 shows the orientation of the control surfaces of the drogue 100as seen when looking down the axis of the drogue 100.

FIG. 16 shows the orientation of the axis of the drogue 100 with respectto a refueling probe as seen from one reference point.

FIG. 17 shows the orientation of the axis of the drogue 100 with respectto a refueling probe as seen from another reference point.

FIG. 18 shows the orientation of a plurality of sensors on the drogue100 with respect to a refueling probe as seen from one reference point.

FIG. 19 shows the orientation of other sensors on the drogue 100 withrespect to a refueling probe as seen from another reference point.

FIG. 20 shows another embodiment of the invention, where the location ofthe refueling drogue is determined based on angles between the refuelingaircraft and the refueling drogue.

FIG. 21 shows an exemplary embodiment of a conventional refuelingdrogue.

DETAILED DESCRIPTION OF SOME OF THE EMBODIMENTS

In a first embodiment of the present invention, as shown in FIG. 1,there is a refueling drogue 100 comprising a rotatable mass 200mechanically coupled to an air turbine 300, such that when the refuelingdrogue 100 is placed in an air stream 900 that flows past the refuelingdrogue 100, air 910 is inducted into the drogue 100 and passes the airturbine 300 rotating the air turbine 300 and imparting a rotation ontothe rotating mass 200 to produce a gyroscopic effect that effectivelypassively stabilizes the refueling drogue 100 as it is being draggedthrough the air behind a refueling aircraft 1000, such as a KC-135and/or A-6 refueling aircraft and/or KC-130 and/or rotary wing refuelingaircraft 1000 as shown in FIG. 2. The particular details of the presentinvention will now be described.

FIG. 2 shows a schematic of the refueling drogue 100 according to thepresent invention being utilized to refuel a receiver aircraft 2000 by atanker 1000. In FIG. 2, it may be seen that a refueling hose 800 extendsfrom the tanker 1000 and is connected to refueling drogue 100. Refuelingdrogue 100 is further connected to refueling probe 2100 extending fromthe receiver aircraft 2000. In the first embodiment of the invention,once the refueling probe 2100 of the receiver aircraft 2000 is capturedin the refueling drogue 100, aviation fuel may be transferred from thetanker 1000 through the refueling hose 800, through the refueling drogue100, and then through the refueling probe 2100, and into tanks (notshown) in the receiver aircraft 2000. In the first embodiment of theinvention, the refueling drogue 100 is adapted to physically connect tothe refueling probe 2100. Connection can be performed in someembodiments per military standards. In the first embodiments of theinvention, the refueling hose 800 is approximately three inches ininterior diameter, while in other embodiments, it is approximately twoinches or four inches in interior diameter. In some embodiments, thehose is about 2.375, 2.625 and 2.875 inches in interior diameter. Thus,some embodiments of the present invention may be practiced with hoses ofdifferent sizes depending on the desired maximum fuel off loads of therefueling aircraft.

The refueling drogue 100 may be effectively passively stabilized byrotating a mass 200 in the refueling drogue 100 at a sufficient speed toproduce a gyroscopic effect that will result in the refueling probe 100being effectively passively stabilized as it is pulled through theatmosphere behind the refueling aircraft 1000. The resulting angularmomentum may be harnessed to fix the drogue's orientation in space, thusstabilizing the drogue. Based upon the principle of gyroscopic motion,the amount of disturbance torque that the drogue can reject is directlyrelated to the angular momentum of the rotating mass 200 (the greaterthe momentum, the greater the amount of disturbance torque the drogue100 can reject), where angular momentum may be increased by increasingthe spin speed and/or the polar moment of inertia (mass distribution) ofthe rotating mass. By rotating the mass 200, a sufficient angularmomentum can be achieved so that the drogue 100 may sufficiently rejectdisturbance forces and thus effectively passively stabilizing the drogue100. That is, the refueling drogue 100 tends to have a fixed orientationin space and is capable of effectively rejecting a disturbance moment(such as turbulence), thus, providing a substantially stable referencehose for the refueling drogue 100 due to the gyroscopic effect of therotating mass. By “stabilized,” it is meant that the disturbanceresponse of the drogue 100 is significantly reduced. By way of example,the angular displacement of the longitudinal axis of the drogue 100 dueto turbulence can be reduced. By “passively stabilized,” it is meantthat the refueling drogue 100 may be stabilized without the need ofcontrol surfaces or other surfaces such as rudders and/or elevators,that alter the orientation and/or position of the refueling drogue 100(or more precisely, physically impart a force or moment on the refuelingdrogue to counter the effects of turbulence, etc., on the refuelingdrogue 100 to substantially fix its angular orientation in space).

In a first embodiment of the present invention, the refueling drogue 100may be configured to harness an air stream 900 flowing past therefueling drogue 100 due to the forward velocity of the drogue 100 as itis dragged through the atmosphere to spin the rotating mass 200 toobtain the gyroscopic effect to passively stabilize the refueling drogue100. Air stream velocities may be below 80 KEAS, 80 KEAS, 100 KEAS, 150KEAS, 200 KEAS, 250 KEAS, 300 KEAS, 350 KEAS, 400 KEAS, or more, or anyspeed or range of speeds therebetween in increments of 1 KEAS, and istypically a function of the forward velocity of the refueling aircraft1000.

Source of Rotation of the Rotatable Mass

In the first embodiment of the invention, the refueling drogue 100includes an air turbine 300 that when exposed to the relative airstream, rotates the rotatable mass 200 as a result of the aerodynamicforces on the air turbine 300. In a first embodiment of the presentinvention, as shown in FIG. 1, air 910 from air stream 900 is inductedinto the refueling drogue 100 and directed past the air turbine 300,which in some embodiments of the invention, may be configured much likea fan, and then exits the refueling drogue 100 out an exhaust port 130and back into the air stream 900. Because the air turbine 900 ismechanically connected to the mass 200, (in the embodiment shown in FIG.1, the air turbine is directly mounted on the rotatable mass 200) therotation of the air turbine 300 is imparted onto the mass 200 which issupported by bearings 220, thus permitting the mass 100 to rotate aboutthe centerline of rotation 210 of the rotating mass.

It is noted that some embodiments of the present invention can bepracticed utilizing compressed air that is passed by the air turbine 300to impart the rotation onto the rotating mass 200. Thus, in someembodiments of the invention, a ram air device may be utilized tocompress the air to a sufficient degree such that when the air ispermitted to expand in proximity to the air turbine 300, the air turbinerotates and a rotation is imparted onto the mass 200.

As can be seen from FIG. 1, a first embodiment of the present inventionmay be practiced with the air turbine 300 inside the refueling drogue100. That is, the air turbine in some embodiments of the invention maybe internal to the refueling drogue 100 in a manner that is, by way ofexample, analogous to the turbine of a conventional jet engine. However,it is noted that in some embodiments of the present invention, as shownin FIG. 3, the air turbine 300 may be located on the outside therefueling drogue 100. Thus, in some embodiments of the presentinvention, the blades 300 can extend from the refueling drogue 100, asshown in FIG. 3. In yet further embodiments of the present invention, aportion of the air turbine 300 may be both located inside the refuelingdrogue and outside of the refueling drogue. In yet further embodiments,a plurality of air turbines may be used, some of which may be locatedinside the drogue 100 and some on the outside of the drogue 100.

In some embodiments of the present invention, the basket 110 thatextends from the rear of the refueling drogue is configured such thatthe basket will rotate, thus imparting a rotation onto the body of therefueling drogue and/or the rotating mass 200 portion of the refuelingdrogue.

It is noted that the present invention may be practiced with a varietyof types of air turbines 300. In the first embodiment of the invention,as shown in FIGS. 1 and 3, the air turbine 300 can comprise a pluralityof radially extending blades and/or vanes that serve to capture energyfrom the air stream 900/910 passing through the blades in a manner quitesimilar to the blades of a conventional bladed fan or windmill. However,in other embodiments of the present invention, the air turbine 300 cancomprise a plurality of passages (holes, slots, spaces, bores, etc.) ina body, the air turbine 300 having a configuration such that when air ispassed through the passages, a rotation is imparted on the air turbine300. By way of example only and not by way of limitation, a air turbine300 having a radial turbine configuration as shown in FIG. 4, may beused to practice the invention (as will be discussed in greater detailbelow). Some embodiments of the present invention may be practiced withany device that may enable energy to be extracted from an air stream tocreate a rotational moment that may be used to rotate and/or assist inrotating the rotating mass 200. Indeed, in some embodiments of thepresent invention, the air turbine 300 may comprise a disk having aplurality of angled bores through the disk at angles such that when airtraveling in the axial direction towards the disk passes through thebores, a rotational moment is imparted on the disk, which then may beimparted on the rotating mass 200.

As mentioned above, a first embodiment of the present invention mayutilize a radial turbine (which may be of a configuration commonlyreferred to as a squirrel cage) as the air turbine 300 to impart arotation on the rotating mass 200. As can be seen from FIGS. 4-5, theradial turbine 350 may be aligned with its axis of rotation 210 parallelor substantially to the direction of the air stream 900. In theembodiment shown in FIG. 4, air 910 from the air stream 900 entersthrough air inlets 120 facing the air stream 900. This air is directedinto a cavity 360 in the radial turbine 350. The air then passes throughslots 370 in the radial turbine 350 and then through passageways 130arranged axially around the exterior of the refueling drogue 100 leadingto the exterior of the drogue 100. The configuration of the slots 370 inthe radial turbine 350 and/or the configuration of the drogue 100 issuch that passage of the air through the slots imparts a rotation ontothe radial turbine. In a first embodiment, the slots 370 are spacedabout every 18 degrees around the circumference of the radial turbine350, although in other embodiments, the slots may be spaced differently.

In the embodiment shown in FIG. 4, the rotating mass 200 is the radialturbine 350. That is, the radial turbine 350 is of sufficient design(mass, geometry, etc.) such that as it rotates, it may produce asufficient gyroscopic effect on the refueling drogue 100 sufficient topassively stabilize the drogue. However, it is noted that in otherembodiments of the present invention, the radial turbine 350 may bemechanically connected to a separate rotating mass 200.

It is noted that in some embodiments of the invention, the air turbine300 may utilize any type of surface/body that may extract mechanicalenergy from an air stream 900 flowing past the refueling drogue 100(including the inducted air 910). Thus, in some embodiments of thepresent invention, the air turbine 300 may simply have a plurality ofsurfaces that, when exposed to an air stream 900 having a relativevelocity to the refueling probe in excess of a certain value, areadapted to rotate and thus rotate the rotatable mass 200 as a result ofaerodynamic forces on the surfaces. In some embodiments of theinvention, these surfaces may be lifting surfaces (L/D greater than 1),may be drag surfaces (L/D less than 1), or a combination of liftsurfaces and drag surfaces.

It is further noted that in some embodiments of the present invention,the air turbine 300 may utilize variable pitch surfaces/blades/vanes,etc., so that the pitch of the surfaces/blades/vanes may be changed, forexample, to maximize the energy extracted from the air flow 900 and/orreduce drag, etc. Some embodiments of the present invention may beutilized by varying the aerodynamic geometry of theslots/protrusion/holes in the air turbine 300 as well. By way of exampleand not by way of limitation, shutters may be placed inside the slots ofthe radial turbine 350 and/or placed on the outside and/or on the insideof the radial turbine 350.

Still further, other embodiments of the present invention may utilize adevice that varies the airflow 910 into the refueling drogue 100 and/orexiting the refueling drogue 100. Thus, some embodiments of the presentinvention may be practiced with any means that can be utilized to varythe amount of airflow/velocity past the air turbine 300. This may permitthe angular speed and/or angular momentum of the turbine to becontrolled. In some embodiments of the invention, the speed/momentum maybe controlled from 0 revolutions per minute to a maximum value, whichmay be determined by the velocity at which the drogue In yet anotherembodiment of the present invention, any device that varies a physicalproperty of the air 910 traveling into/through/exiting the refuelingdrogue 100 (e.g., mass flow, velocity, temperature, pressure, etc.) maybe used to practice the invention.

It is noted that while the embodiments shown in the figures are depictedas having a air turbine 300 with a centerline of rotation 210substantially parallel to the centerline 105 of the drogue 100 and/orthe direction of air flow 900, other embodiments of the presentinvention can be practiced where the centerline of rotation 210 of theair turbine is not parallel to the just mentioned features. By way ofexample, the air inlets 120 might channel the air 910 in a directionnormal to the direction of the air stream 900, and thus, in the case ofa radial turbine, the radial turbine may have its centerline of rotation210 normal to the direction of the air stream 900. In such anembodiment, gears might be utilized to connect the radial turbine to arotating mass 200 if it is desirable that the centerline of the rotatingmass be parallel to the centerline of the refueling drogue 100.

In some embodiments of the present invention, where the air turbine 100extends away from the refueling drogue, as shown by way of example inFIG. 3, the air turbine 300 may be configured to retract towards therefueling drogue and extend outward from the refueling drogue such thatthe outer diameter of the air turbine 300 may be varied. In theembodiment shown in FIG. 3, the blades of the air turbine 300 may bemounted on hinges 310 and connected to actuators 320 such that theactuators may retract and/or extend the blades. Still further, theblades may also be extended by centrifugal force and retracted by, forexample, using springs and/or an actuator and/or by shutting off the airturbine. Such an embodiment might be practiced in the case where therefueling drogue is retracted into the refueling aircraft 1000 and/or acontainment vessel on the refueling aircraft 1000. In yet furtherembodiments of the present invention, the air turbine 300 may beconfigured to retract substantially completely inside the refuelingdrogue 100, while in yet further embodiments of the present invention,the air turbine 300 may be configured to retract completely inside therefueling drogue. In some embodiments of the present invention, the airturbine 300 may be configured to only retract a partial distance fromits full outer diameter.

Some embodiments of the present invention will utilize a refuelingdrogue basket 110, as shown, for example in FIGS. 1 and 4. In someembodiments of the invention, the basket 110 comprises struts 112 thatconnect the canopy to a canopy and/or parachute 114, where the canopyand/or parachute 114 may provide additional passive stability to thedrogue 100. This basket may help passively stabilize the refuelingdrogue 100 and/or enhance capture of the refueling probe 2100 due to thefunneling effect of the basket. Still further, the struts 112 may serveto act as a final guide for the refueling probe into the socket of therefueling drogue 100. Additionally, the basket 110 may act as a liftingsurface. Some embodiments of the present invention may be configuredsuch that the air turbine 300 is configured that the outer diameter isless than the greatest exterior diameter of a refueling drogue basket110 when the refueling drogue basket is fully deployed and/orsubstantially fully deployed. In such an embodiment, the refueling probe2100 of the receiver aircraft 2000 and/or the receiver aircraft itselfmight be better protected because the refueling probe would more likelycontact the exterior diameter of the refueling drogue basket 110 insteadof contacting the air turbine 300.

It is noted that in some embodiments of the present invention, theharnessed air stream may be used in conjunction with another means ofrotating the rotatable mass 200. That is, some embodiments of thepresent invention need not be practiced by rotating the mass 200 byexclusively harnessing the air stream relatively flowing past therefueling drogue 100. Indeed, other embodiments of the present inventioncan utilize a rotating mass that is rotated utilizing a means that donot include harnessing the relative air stream 900. By way of example,other sources of power may be used to rotate the mass 200. For example,hydraulic power, pneumatic power, electrical power (e.g.,battery/rechargeable battery), magnetic power, chemical power (e.g.,combustion), etc. may be used to rotate the rotatable mass 200.

Rotatable Mass

In some embodiments of the present invention, the refueling drogue maybe adapted to be effectively passively stabilized when the rotating mass200 rotates with a speed of about 1,000-20,000 revolutions per minute.In other embodiments of the present invention, the refueling drogue maybe stabilized with a mass that rotates at a speed anywhere in the rangeof about 100 revolutions per minute to about 50,000 revolutions perminute, and any ranges therebetween in increments of 1 revolution perminute. In yet other embodiments of the present invention, rotationspeeds may range from between about 3000 to about 10,000 and/or about8,000 to about 15,000 revolutions per minute. It is noted that in someembodiments of the present invention, the gyroscopic effect may beincreased by increasing the speed at which the rotating mass 200rotates. In other embodiments of the present invention, the gyroscopiceffect may be increased by increasing the mass that is rotated. In stillfurther embodiments of the present invention, the gyroscopic effect maybe increased by increasing the radial distance that the mass ispositioned from the centerline of rotation 210 (which may be coaxialwith the centerline of rotation of the air turbine 300) of the mass 200.Thus, the gyroscopic effect may be varied by varying the moment ofinertia of the rotating mass 200. In yet other embodiments of thepresent invention, the gyroscopic effect may be increased by varying allof the just mentioned variables. It is further noted that in someembodiments of the invention, an increased gyroscopic effect may beobtained by increasing some of these variable and decreasing other ofthese variables. By way of example and not by way of limitation, someembodiments of the invention might be practiced by utilizing arelatively low mass that rotates at a high rotation speed. While inother embodiments of the invention, the mass might rotate at arelatively low rotation speed but be a relatively high radial distancefrom the centerline of rotation. Some embodiments of the presentinvention may be practiced with a rotatable mass 200 that comprisesabout 10% to about 20% of the total weight of the refueling drogue 100,although other embodiments may be practiced with rotatable masses thatare below this range or above this range. Indeed, in some embodiments ofthe present invention, this range might be a minimum weight of the mass200.

It is noted that the centerline of rotation 210 of the rotating mass200, in some embodiments of the invention, may be coaxial with thecenterline 105 of the drogue 100, while in other embodiments thecenterline 210 may be parallel with the direction of the air stream 900,while in other embodiments the centerline 210 may past through thecenter of gravity of the refueling drogue 100. In yet other embodiments,the centerline 210 of rotation may be positioned in any orientation thatwill permit the rotating mass 200 to create a sufficient gyroscopiceffect that will effectively passively stabilize the refueling drogue100.

Some embodiments of the present invention may include a plurality ofrotatable masses 200, as can be seen in FIGS. 6 and 7, adapted tosubstantially stabilize the refueling drogue via a gyroscopic effect ofthe rotating masses 200. In one embodiment shown in FIG. 6, centerlinesof rotation 210 of the rotating masses may be parallel to one another.In other embodiments, such as that shown in FIG. 7, the centerlines ofrotation 210 of the masses 200 may be coaxially aligned. In otherembodiments of the invention, respective centerlines of rotation of therotating masses may be uniformly arrayed about the center mass 190 ofthe refueling drogue. However, other embodiments of the presentinvention can be practiced wherein the centerlines of rotation are notcoaxial with one another and/or not parallel to one another and/or notarrayed about the center of mass 190. For example, the centerlines mightbe about the polar axis of the refueling drogue and about an axisorthogonal to the polar axis of the refueling drogue. In someembodiments, all the masses may rotate counterclockwise or clockwise. Insome embodiments of the invention, any distribution of rotating masses200 may be used if the drogue can be effectively passively stabilized.

It is noted that in some embodiments of the present invention, the airturbine 300 may be configured to support the rotating mass and/or atleast partially support the rotating mass 200, as shown in FIG. 8. Insome embodiments of the present invention, the air turbine-rotating masscombination may be located completely inside the refueling drogue 100 orpartially inside or outside the refueling drogue 100 or completelyoutside the refueling drogue 100. Thus, in some embodiments of thepresent invention, the rotating mass 200 may be configured to haveaerodynamic properties to be conducive to the flow of air in the airstream 900 over and/or across the air turbine-rotating mass combination.

Some embodiments of the present invention may be practiced by rotatingthe entire refueling drogue 100. In such an embodiment, theconfiguration of the refueling drogue 100 could be configured such thatthe spinning of the refueling drogue 100 produces a sufficientgyroscopic effect to effectively stabilize the refueling drogue 100. Insome embodiments of the present invention, the entire refueling droguebody is configured to rotate about the refueling hose 800 or a component810 that is connected to and/or is part of the refueling hose 800 and/orconnected to and or is part of the refueling drogue 100 to permit thedrogue 100 to rotate By refueling drogue body, it is meant the most orall of the drogue 100, and may or may not include, for example, theconnector 810 that connects the drogue 100 to the refueling hose 800 andmay or may not include the basket 110. Thus, in some embodiments of thepresent invention, the refueling drogue 100 includes an adapter or othercomponent that will permit the refueling drogue to rotate relative tothe refueling hose 800. In some embodiments of the invention, this mayinclude an adapter positioned between the refueling hose 800 and therefueling drogue 100. However, in other embodiments of the presentinvention, the refueling drogue body may be prevented from rotatingrelative to the refueling hose so that, as noted above, the rotatingmass 200 may be configured to rotate relative to the refueling droguebody and/or the refueling drogue basket 110. Other embodiments of thepresent invention might include rotating only the basket 110.

Another form of passive stabilization which may reduce the amplitude ofthe response of the lateral displacement of the drogue 100 to turbulencemay be achieved by installing aerodynamic surfaces 580 as shown in FIG.11 on the refueling hose/drogue connector 810 and/or on the hose 800and/or on the body of the refueling drogue 100. It is believed thatthese surfaces may provide a similar type of damping force as thatobtained by a horizontal and/or vertical stabilizer on a conventionalaircraft. In a first embodiment, these surfaces may be placed in pairswhich, in some embodiments, are placed orthogonal to each other. In oneembodiment, the surfaces lie in planes that intersect or substantiallyintersect the axis 820 of the refueling hose 800 (and/or an extendedaxis of the refueling hose 800). In some embodiments, the surfaces maybe aerodynamically shaped and may be capable of being retracted forstowage. It is noted that these surfaces may be located on the refuelinghose 800 and/or on the connector portion 810 and/or on the drogue 100body.

Active Control

As noted above, the present invention utilizes the spinning motion ofthe rotatable mass 200 to effectively passively stabilize the drogue100. However, other embodiments of the present invention may be utilizedwith an active control system that actively controls the refuelingdrogue about an arbitrary selectable reference line. By active control,it is meant a control system that may impart forces on the drogue 100and/or the hose 800 to control/regulate the location of the refuelingdrogue 100 and/or the hose 800. In some embodiments, the force may beorthogonal to the velocity of the air stream. In some embodiments, itmay be used to established a substantially fixed position of the droguewith respect to the refueling aircraft. Active control may additionallysuppress lateral translations of the drogue 100 and/or the refuelinghose 800 in response to disturbances/turbulence. In such embodiments,the effect of spinning the rotatable mass 200 may be combined withactively controlling the motion of the drogue 100. Active control may bepracticed, in some embodiments of the present invention, to counteractthe effects of wind gusts and/or cross winds, etc. (typically moderateto high frequency gusts/cross-winds) that may affect the relativeposition of the refueling drogue 100, for example, in relation to therefueling aircraft and/or the velocity vector through the air. In afirst embodiment of the invention implementing an active control system,as shown in FIG. 9, the active control system includes a plurality ofcontrol surfaces 600 which may include movable portions 610 which may bedriven by actuators controlled by an active control system computer 620,which in some embodiments of the present invention, may be located inthe refueling aircraft 1000, while in other embodiments of the presentinvention, may be located on the refueling drogue 100, and in furtherembodiments of the present invention, may be spaced between both places.In the first embodiment of the present invention, the movable surface610 are movable tabs that function in a similar matter to an aircraftelevator and/or rudder. In some embodiments, the control surfaces 600may be as according to U.S. Pat. No. 2,582,609, the contents of which isincorporated herein in its entirety. It is further noted that the activecontrol system might include additional control surfaces as well, suchas control surfaces 1600 that may include movable portions 1610, such asthat shown in FIG. 12.

It is noted that while the active control system of the presentinvention is described in terms of maintaining a “fixed” or “desired”orientation of the refueling drogue and/or maintaining a “fixed” or“desired” position/angle of the refueling drogue, which might be areference angle and/or a reference position, etc., the active controlsystem, as would be readily understood by one of ordinary skill in theart, in actuality, returns the refueling drogue 100 to its positionprior to being displaced due to disturbances and/or substantiallyminimizes what otherwise would be a large displacement. That is, therefueling drogue, in some embodiments of the present invention, will notbe able to maintain a “fixed” position or a “desired” orientation, butwill instead be able to return the drogue to the drogue's priorposition/orientation/angle quickly enough and/or to minimize thedisplacement of the drogue 100 such that the refueling drogue may beactively controlled. In one embodiment of the present invention, theactive control system reduces the translational movements of the drogue100 in response to a disturbance such that most or all of thedisplacement of the drogue is minimal enough that displacement of thedrogue 100 does not interfere with aerial refueling and/or create ahazard to the aircraft being refueled. In some embodiments of theinvention, disturbances or oscillations are a result of atmosphericturbulence and/or the bow wave effect and/or an impact of the drogue bya refueling probe of a receiver aircraft while attempting to dock withthe drogue.

The active control system may be configured so that the position of thedrogue may be maintained to a substantially fixed orientation relativeto the refueling aircraft 1000 or another reference point. In someembodiments, the orientation may be maintained in moderate turbulence,to within about twelve inches, while in other embodiments theorientation may be maintained within six inches, and in still furtherembodiments, the orientation may be maintained to within a few inches.It is noted that in some embodiments of the present invention, howtightly the position of the refueling drogue 100 may be maintained is afunction of the size and/or the configuration of the refueling drogue100, such that configurations of some refueling drogues will be moreconducive to position maintenance than others. Thus, the just mentionednumbers may vary upward and/or downward, depending on the configurationof the refueling drogue utilized to practice the invention.

In a first embodiment of the invention, the control surfaces 600 arelocated in pairs such that the pairs are substantially orthogonal to oneanother as shown in FIG. 9, although in other embodiments of the presentinvention, the control surfaces need not be orthogonal. In someembodiments of the invention, the control surfaces are located, when thedrogue 100 is in a steady level flying condition and not rotating, in avertical plane (i.e. a plane lying parallel to the direction of gravityand parallel to the direction of the air stream 900) and in a horizontalplane (as judged from the horizon). However, in other embodiments of thepresent invention, the control surfaces may be located in planes otherthan the just mentioned planes. By way of example and not by limitation,the control surfaces 600 may form a canted cross shape such as thatshown in FIG. 15 when viewed down the longitudinal axis of the refuelingdrogue 100. Thus, some embodiments of the present invention may bepracticed with orthogonal control surfaces located in variousorientations about the refueling drogue. Still further, as noted above,other embodiments of the present invention may be practiced with controlsurfaces that are not orthogonal to each other. By way of example andnot by limitation, the control surfaces 600 may form an X shape whenviewed down the longitudinal axis of the refueling drogue 100. Indeed,in other embodiments of the present invention, three control surfacesmay be used. Such an embodiment might form a Y shape (where the “leg”and “arms” of the Y are equal in length and spaced equally and/or wherethey are not equal in length/size and/or not spaced equally). It isnoted that it is believed that in some embodiments of the presentinvention, orthogonal control surfaces may make implementation of theactive control system according to the present invention easier, as thenon-orthogonal control surface arrangement may require the controlsystem to account for the non-orthogonality of the surfaces.

It is noted that in some embodiments of the present invention, theactive control system can be configured to actively control therefueling drogue 100 for substantially any rotation angle of therefueling drogue, and thus the control surfaces, from the just describedhorizontal plane and/or the vertical plane. Some embodiments may utilizea sensor 630 to measure the rotation angle γ of the refueling droguewith respect to a fixed direction (such as the direction of gravity),and thus the rotation angle γ of the control surfaces 600 with respectto the fixed direction. Some embodiments may utilize a micro electricalmechanical system accelerometer triad and its associated electronics inorder to resolve the rotation angle γ. By way of example and not by wayof limitation, a pendulum-like gravity vector sensor may be utilized asthe vector sensor 630. In other embodiments of the present invention, agyroscope may be utilized to determine the rotation angle of therefueling drogue 100, etc. Still further, in other embodiments of thepresent invention, any device that may be used to determine the rotationangle of the refueling drogue so that the control surfaces may beutilized to actively control the refueling drogue, may be utilized topractice the present invention. By way of example, a shaft encoder mightbe used. Thus, as the refueling drogue rotates, the orientation of thecontrol surfaces 600/610 with respect to the horizontal and verticalplanes and/or any other appropriate reference axis can be determined,and movements of the control surfaces can be adjusted accordingly.

One embodiment of the present invention may utilize the active controlsystem to change the vertical and/or horizontal position of therefueling drogue. In some embodiments of the present invention, theactive control system may permit the refueling drogue 100 to maintain asubstantially fixed orientation relative to the refueling aircraft 1000when the refueling aircraft is flying at substantially constant altitudeof air speed and/or heading. However, other embodiments of the presentinvention may be utilized to maintain a substantially fixed orientationof the drogue 100 relative to the refueling aircraft, even thought herefueling aircraft is not flying at a substantially constant altitude,air speed, and/or heading.

An embodiment of the present invention that utilizes the active controlsystem may be configured to regulate the location of the refuelingdrogue 100 based on measured angles between an axis 820 through thecenter of the refueling hose/line 800 at a location where the refuelinghose connects to the drogue 100 and a reference axis. This referenceaxis may be based on, for example, the direction of gravity and/or thedirection of air flow V of the air stream 900. In other embodiments,this reference axis may be based on the control surfaces 600/610 of therefueling drogue.

In a first embodiment of the present invention, two angles are measuredin planes orthogonal to one another, the angles being measured inreference to control surfaces 600. The first angle, θ, represents theangle between the axis 820 of the refueling hose and the velocity vectorV in the plane of a control surface, which, in FIG. 15, is controlsurface 601, while the second angle, ψ, represents the angle between theaxis 820 of the refueling hose and the velocity vector V in the plane ofa control surface, which, in FIG. 15, is control surface 602, hose. Thiscan be seen in FIGS. 13 and 14, thus showing the angle θ of therefueling hose 800 relative to the direction of air flow V, while FIG.14 shows the angle, ψ, of the refueling hose 800 relative to thedirection of air flow V. However, it is noted that other embodiments ofthe present invention may measure angles that are not orthogonal to oneanother and/or not in the just mentioned planes and/or not in the planesof the control surfaces. It is further noted that in some embodiments ofthe present invention, the refueling hose 800 may rotate with therefueling drogue 100 and/or independently of the refueling drogue. Byutilizing a rotation sensor, such as that described above, the rotationangle γ of the refueling hose 800 at section 810 may be determinedrelative to the reference axis, as exemplary depicted in FIG. 15.

Still further, by determining this rotation angle γ, the measured anglesθ and ψ may be converted to a refueling hose 800 pitch angle θ′ and arefueling hose yaw angle ψ′, via standard coordinate transformation, ascan be readily seen from FIG. 15. Thus, because the displacement of thedrogue relative to the refueling aircraft is proportional to the pitchand yaw angles of the refueling hose, the displacement of the drogue 100may be controlled by regulating the pitch and yaw angles based uponmeasurements of angles θ and ψ. Again, it is noted that while theembodiment depicted in FIG. 15 shows the angles and the control surfacesin orthogonal relationship to one another, other embodiments may bepracticed where they are not in orthogonal relationship to one another.

This embodiment may be understood by relying on the phenomenon that,because the portion of the refueling hose 800 on the end that attachesto the refueling drogue 100 can be considered a quasi-rigid body, theorientation of the axis 820 through the center of the refueling hose 800at the point where the refueling hose connects to the refueling drogue100 will change in proportion to changes in at least the location of therefueling drogue 100. Thus, the lateral displacement of the droguerelative to the refueling aircraft is proportional to the angles θ and ψof the axis of the hose, as discussed above. Consequently, thisdisplacement may be controlled by regulating the angles θ and ψ basedupon their measurements. This is somewhat analogous (although thisembodiment should not be considered limited by the analogy) todetermining the position relative to the towing boat of a water skierbased on the angle of the rope.

The angles θ and ψ of the centerline 820 of the refueling hose 800 maybe measured on any two respective planes, providing that there is a wayto link the orientation of the planes to the orientation of the controlsurfaces of the refueling drogue 100 so that the active control systemcan adjust the control surfaces to regulate the position of the drogue100. Again, it is noted that in some embodiments of the presentinvention, the angles θ and ψ of the refueling hose 800 may be measuredon planes orthogonal to the planes on which the control surfaces thatregulate those angles lie. In some embodiments, this may permit thelocation of the drogue 100 to be regulated without reference to thehorizontal plane and/or the vertical plane. In yet other embodiments,angles measured in any plane that will allow the active control systemto regulate the location of the refueling drogue 100 may be used topractice the invention.

It is noted here that when utilizing the term “measured,” the termincludes determining the angle utilizing sensors located on the planeson which the angles lie as well as sensors located elsewhere andutilizing a coordinate transformation to measure the angle at theplanes.

In a first embodiment of the present invention, the control system isconfigured to substantially maintain the angle θ and/or the angle ψ ofthe axis 820 of the refueling hose 800 at respective constant referenceangles, and thus the control system may be configured to substantiallymaintain the pitch angle θ′ and/or the yaw angle ψ′ of the axis 820 ofthe refueling hose 800 at respective constant reference angles. In someembodiments of the present invention, the reference angle of the yawangle ψ′ of refueling hose axis 820 is zero degrees or substantiallyzero degrees from the vertical plane, although it could be other anglesas well. In contrast, an embodiment of the present invention may utilizea pitch angle that is a non-zero angle from a reference planecorresponding to the horizontal plane, as well as a zero degree angle orsubstantially zero degree angle. That is, the axis 820 of the refuelingdrogue hose 800, in some embodiments of the present invention, typicallyhas a non-zero pitch angle due to the effects of gravity and/or theaerodynamic forces on the refueling drogue at steady level flight and/orthe bow wave effect from the receiver aircraft, and thus the pitch angleθ′ of the refueling hose axis may be a non-zero angle. Still further, insome embodiments of the present invention, the pitch angle maintained bythe control system may be purposely variable from the angle that wouldnormally result from aerodynamic forces and/or the effects of gravity.By way of example and not by way of limitation, when refueling rotarywing aircraft, the pitch of the refueling hose axis may be adjusted to,for example, “lower” the position of the refueling drogue 100 from theposition that it might otherwise be located, to, for example, ensurethat there is enough clearance between the refueling hose and/or drogueand the rotors of the rotary wing aircraft. In such an embodiment, thepresent invention may be practiced to achieve the same result and/or thesimilar result as is achieved by practicing the concept of a variablespeed drogue. Still further, some embodiments may be practiced where theposition of the drogue 100 may be controlled in a manner that is notdependent on the speed of the drogue 100 through the air, at least forspeeds at and above the speed at which the refueling aircraft 1000 mustfly to maintain altitude and/or maintain a sufficient horizontalextension of the refueling hose 800. By way of example, at speeds aboveabout 60 KEAS. In some embodiments of the present invention, the activecontrol system may be utilized to practice the invention with anycomponents or systems that will enable angles θ and ψ the axis of therefueling hose to be substantially controlled. In yet furtherembodiments, the present invention can be practiced with anydevice/system that will permit the position of the drogue 100 to besubstantially controlled.

According to a first embodiment of the present invention, as notedabove, active control of the refueling drogue to maintain a givenposition is achieved by controlling angles of the axis of the refuelinghose 800 with respect to a reference axis. Such a reference axis, asnoted above, might be determined based on the direction of the airstream 900. Thus, some embodiments of the present invention may bepracticed with sensors 640 that are configured to measure an anglebetween the axis of the refueling hose 800 and a direction of an airstream 900 flowing past the refueling drogue, thus measuring the anglesθ and ψ of the refueling hose axis 820. In the first embodiment of thepresent invention, the sensors 640 may be angle of attack/side slipsensors. In the first embodiment of the invention, these sensor 640 arepositioned to measure θ and ψ of the refueling hose axis 820 at arefueling hose/drogue connector 810, which, in some embodiments of thepresent invention, is configured to permit portions of the main body ofthe refueling drogue 100 (e.g., the portions aft of the connector 810)to pivot. It is noted that the connector 810 is rigidly mounted to therefueling hose 800, and thus may be part of the refueling hose 800and/or part of the body of the drogue 100. Still further, because theconnector 810 is rigidly mounted to the refueling hose 800, a referenceaxis of the connector 810 can be correlated to the centerline 820 of therefueling hose 800, and thus measurements of the angles θ and ψ of theconnector 810 can be used to measure θ and ψ of the centerline 820 ofthe refueling hose 800. That is, in some embodiments of the invention,the sensors may be positioned anywhere that will permit the angles θ andψ to be measured, whether those sensors be on the refueling hose, theconnector to the refueling hose, or the body of the refueling drogue.

In a first embodiment, the connector 810 is configured to permit themain body of the drogue 100 to freely pivot about the axis of therefueling hose 800 within a range of (when measured from, for example,the centerline 105 of the refueling drogue), such as by way of example,a cone of about 5 degrees, a cone of about 10 degrees, a cone of about20 degrees, a cone of about 30 degrees, 40 degrees, 50 degrees, 60degrees, 70 degrees, 80 degrees and/or 90 degrees, and/or any conehaving an angle there between in about 0.1 degree increments. Thus, insome embodiments of the invention, the pitch and/or yaw angles of therefueling drogue 100 may be independent of the pitch and/or yaw angle ofthe axis 820 of the refueling hose 800.

In the first embodiment, these sensors comprise a rotary vane and shaftthat pivots. The vanes extend into the air stream 900 and are aligned,during operation, by aerodynamic forces to lie parallel to the air speedvelocity vector. The shaft of the vanes is connected to an angle sensorsuch as, by way of example, a rotary potentiometer. In some embodimentsof the invention, the sensors 640 may output an analog electrical signalthat may be used to determine angular deviation from a desired θ and ψangle. In the first embodiment of the invention, the sensors 640, ormore specifically the vanes of the sensor 640, are located such thatthey are substantially orthogonal to one another. Thus, in the firstembodiment, of the present invention, the active control system computer620 is configured to receive signals from the sensors 640 and analyzethese signals and determine what corrective control signals should beoutputted to actuators of the control surfaces 600/610 to return therefueling drogue 100 to the desired pitch angle and/or yaw angle.

It is noted that in other embodiments of the present invention, aninertial measurement unit might be utilized to provide the necessarydata to control the refueling drogue.

It is been found that displacement of the refueling drogue may bedetermined from the angles θ and ψ of the axis 820 of the refueling hose800. These displacements may be proportional to the yaw angle and thepitch angle. This may be determined mathematically utilizing analgorithm based on the following equations:y=f(θ′), andz=g(ψ′), where

-   -   y=a distance in the plane in which the angle θ′ lies,    -   z=a distance in the plane in which the angle ψ′ lies,    -   θ′=the pitch angle of the refueling hose, and    -   ψ=the yaw angle of the refueling hose, where    -   f and g are functions that describe the relation between y and        θ′ and z and ψ′, which in some embodiments may be related to the        length of the refueling hose. Thus, the lateral positions of the        drogue 100 can be controlled by regulating θ′ and ψ′.

In another embodiment of the present invention, the drogue 100 positionmay be measured relative to the refueling aircraft via a sensor and/or aplurality of sensors located on the refueling aircraft. These sensor(s)may be located on a refueling drogue containment vessel, and may bemicrowave or optical sources that scan, in some embodimentscontinuously, over a region which, in some embodiments, is a conicalregion behind the refueling aircraft and/or behind a location of thecontainment vessel, as shown in FIG. 20. The position of the drogue maybe determined by detecting a signal reflected from the drogue, which maybe from a corner reflector and/or a transponder. In other embodiments,the drogue may generate the signal.

A three dimensional position of the drogue may be determined byreceiving the reflected (and/or generated) signal from the drogue. Theposition information may then be used by the active control system toregulate the position of the drogue and/or to suppress unwanted lateralmotion of the drogue. The position of the drogue may also be determinedutilizing the instantaneous angular position of the drogue with respectto the refueling aircraft. That is, as shown in FIG. 20, angles ρ and ξmay be determined and, based on the length of the hose 800, the drogue'sposition may be determined. Such angles may be determined utilizing areceiver on the drogue and/or on the refueling aircraft that demodulatesa signal to obtain information regarding its position. In someembodiments, a carrier signal generated from the drogue and/or therefueling aircraft is modulated with a signal that is indicative of theinstantaneous angle from a reference plane (which may be vertical orhorizontal), the drogue and/or the aircraft detects a maximum of thecarrier signal indicating that the beam is pointing at the drogue and/oraircraft at that instance, the receiver demodulates the carrier at thatpoint, the demodulated signal being indicative of the angle measuredfrom the reference plane. In another embodiment, the distance may bedetermined based on a signal in the carrier signal based on the hoselength. Based on the angles and the distance, the location of the droguecan be determined. Based on the position of the drogue, the activecontrol system and/or the autonomous docking system may regulate themovements of the drogue. Thus, it will be seen that some embodiments ofthe active control system and/or the autonomous docking system(discussed in detail below) may be practiced with any means that willallow the position of the refueling drogue relative to the refuelingaircraft to be determined. Still further, in some embodiments, a GPSand/or a DGPS (differential GPS) may be used to determine the positionof the refueling drogue. It is further noted that the drogue positionmay be measured by sensors that may be on the refueling aircraft and/ormay be on the drogue, and the drogue's position may then be communicatedto the refueling drogue's control system. Additionally, it is noted thatwhile in FIG. 20, angles ρ and ξ are shown measured from the point atwhich the hose 800 contacts the aircraft to the point at which the hose800 contacts the refueling drogue, other embodiments could measure theseangles from different points, and using a coordinate transformation,determine the location of the drogue.

That is, in some embodiments the present invention, the active controlsystem computer 620 may be utilized to determine displacement and/or therelative location of the refueling drogue based on the measured angle θand/or ψ of the refueling hose 800. Thus, in some embodiments, theposition can be utilized to control the drogue 100 so that it willmaintain a desired position. Still, it is noted that in some embodimentsof the present invention, active control can be achieved by simplyregulating the angles θ and ψ of the refueling hose such that therefueling hose pitch angle is maintained at the desired pitch angle andthe yaw angle is maintained as the desired yaw angle.

It is noted that in some embodiments of the present invention, thecontrol surfaces 600 may be configured to retract completely into therefueling drogue 100 or retract substantial distance into the refuelingdrogue 100 and/or otherwise fold around or collapse around the refuelingdrogue 100 or otherwise move towards the refueling drogue 100 so that,by way of example and not by limitation, the refueling drogue 100 can bemore easily stowed. It is further noted that in some embodiments of thepresent invention, these surfaces 600 may be located at the connector810 which may be a hose-drogue pivot point.

The active control system of some embodiments of the present inventionmay be utilized by implementing a control system having circuitry thatutilizes a feedback system and/or iterative system and/or gain and/orerror signals to generate control signals to actively control theposition of the refueling drogue 100. For example, the difference inθ−θ_(ref) and ψ−ψ_(ref), may be treated as errors in such circuitry,where the reference angles are the desired angles of pitch and/or yaw.Still further, in some embodiments of the present invention, a logicroutine may be utilized in the active control system computer 620 tocontrol the control surfaces 600/610 and thus actively control therefueling drogue.

It is further noted that in some embodiments of the present invention,the power utilized to regulate the control surfaces 600/610 might beobtained by utilizing a self contained power source that, by way ofexample and not by way limitation, might be obtained by attaching agenerator or other electrical producing device to the rotating mass 200and/or the air turbine 300 to generate electric power and/or to charge abattery to power electrical actuators/servos of the control surfaces.Indeed, in other embodiments of the present invention, this electricalgenerator might be utilized to power the control systemcomputer/circuits. Still further, in other embodiments of the presentinvention, batteries might be utilized to power the control surfaces. Inyet further embodiments of the present invention, the combination of thetwo might be used. In other embodiments of the present invention, ahydraulic/pneumatic actuators might be used to move the controlsurfaces. In such an embodiment, a hydraulic pump might be attached tothe mass 200 and/or the air turbine 300, where the rotation of the airturbine 300 and/or mass 200 rotates the pump, thus producing hydraulicpower.

As noted above, some embodiments of the present invention can bepracticed with a refueling drogue 100 that is free to pivot about theaxis of the refueling hose 800. However, other embodiments of thepresent invention can be practiced where the refueling hose 800 is notfree to pivot about the axis of the refueling hose 800 while stillimplementing an active control system.

Autonomous Docking

Some embodiments of the present invention may also include an autonomousdocking system. In a first embodiment of the invention, some or all ofthe components of the just described active control system may beutilized to implement the autonomous docking system of the invention. Insome embodiments of the invention, the drogue, which is operating in theactive control mode, switches to the autonomous docking mode (althoughother embodiments can go from a non-active control mode to theautonomous docking mode.) In some embodiments, prior to switching to theautonomous docking mode, the location of the receiver aircraft isestablished via a second set of sensors that are located on the drogue100. These sensors may continuously ‘scan’ for the receiver aircraft.Once its position has been established, the autonomous docking mode maybe entered, the details of which will now be discussed.

The autonomous docking system of the present invention may enable therefueling drogue 100 to be “flown” (e.g., maneuvered under automaticcontrol) to the refueling probe 2100 of a receiver aircraft 2000, which,in some embodiments of the invention, might be an unpiloted aerialvehicle. That is, in some embodiments of the invention, the autonomousdocking system may be utilized to refuel an aircraft that does notmaneuver to insert a refueling probe into the refueling drogue, butinstead flies in a steady level fashion, which may be in formation withthe refueling aircraft. Thus, the drogue 100 may be considered a smartdrogue. In some embodiments of the invention, the receiver aircraft 2000may be flying in relatively loose formation with the refueling aircraft1000. In some embodiments of the invention, the refueling aircraftand/or the receiver aircraft may be a UAV or a UCAV. It is further notedthat in some embodiments of the invention, the refueling aircraft may beunmanned as well, while in other embodiments, personnel on the refuelingaircraft exert authority over the refueling operation (e.g., initiatethe autonomous docking function, abort a docking procedure, etc.)

According to one embodiment of the invention, the autonomous dockingsystem may be configured to vary the position of the refueling drogue100 so that the centerline 105 of the refueling drogue along itslongitudinal axis is coaxially aligned or substantially coaxiallyaligned with a centerline of the refueling probe 2100 of the receiveraircraft 2000 when the aircraft 2000 is not yet in contact with therefueling drogue 100. This may be accomplished, in some embodiments ofthe invention, in the manner discussed below.

The first embodiment of the invention, the autonomous docking system maybe configured to measure angle or a plurality of angles between therefueling drogue 100 and the refueling probe 2100 of the receiveraircraft 2000 and/or, between a location on the refueling drogue 100 anda reference point 2150 (discussed in greater detail below) on the probe2100. In the first embodiment of the invention, this angle (or angles)is (are) measured from a location at or near the receptacle of therefueling drogue 100 that receives the refueling probe 2100 to alocation at or near the tip of the refueling probe 2100, and/orlocations of known orientation from those locations, such as, forexample, locations 700 and 2150 shown in FIGS. 16 and 17 (discussed ingreater detail below) and, by using geometry, for example, convertingthese measured angles to angles that would be indicative of ameasurement from the location at or near the receptacle of the refuelingdrogue 100 to a location at or near the tip of the refueling probe 2100.In some embodiments of the invention, the autonomous docking system maybe configured to measure a plurality of angles between the refuelingdrogue 100 and the refueling probe 2100 of the receiver aircraft 2000.One of these angles may be an angle λ measured in a plane (the firstangle), which may be orthogonal to a control surface (e.g., the sameplane as θ in FIG. 15), as shown in FIG. 16, which represents a sideview of the drogue 100 and the probe 2100, and another angle η may be anangle measured in another plane (the second angle), which may beorthogonal to the plane on which the first angle lies, as shown in FIG.17, which represents a top view of the drogue 100 and the probe 2100. Itis noted that in other embodiments of the invention, these angles may bemeasured in other planes that are orthogonal to one another, as well asin planes that are not orthogonal to one another.

It is noted that in some embodiments of the invention, the autonomousdocking system may utilize the control surfaces 600/610 on the connector810 to vary the position of the refueling drogue 100, while in otherembodiments, the autonomous docking system may utilize the controlsurfaces 1600/1610 shown in FIG. 12, which may be located on therefueling drogue body, to practice the invention. Such control surfacesmay be utilized to better regulate the location of the drogue 100 bodyin the case were the connection 810 includes a pivot component, althoughin other embodiments, the surfaces 600.610 may be used even if theconnection 810 has a pivot component. In some embodiments, any controlsurfaces located anywhere may be used to practice the autonomous dockingembodiment of the present invention, as long as the drogue 100 may beflown to the refueling probe 2100 of the receiver aircraft 2000.

In some embodiments of the present invention, the first angle and thesecond angle may be measured on planes orthogonal to the planes on whichthe control surfaces that regulate those angles lie. In yet otherembodiments, angles may be measured in any plane that will allow theautonomous docking system to regulate the location of the refuelingdrogue 100 to achieve docking with the refueling probe 2100 may be usedto practice the invention. Still further, angles may be measured fromany location on the refueling drogue 100 and/or the refueling aircraftto any location on the refueling probe 2100 and/or the receiver aircraft2000 that will permit autonomous docking to be performed.

It is noted that in some embodiments, it may not be possible to locate asensor along the drogue 100 axis 105 since this area may be needed to bekept clear to permit the probe to connect to the drogue 100. Thus, inone embodiment, the angle λ can be measured using a pair of anglemeasuring sensors (as described above) located at diametrically oppositepoints on the drogue 100. These sensors may lie in the planes of thecontrol surfaces. Each sensor may measure an angle λ₁λ₂ respectively, asshown in FIG. 18. The true angle λ may be obtained by averaging thesetwo angles. A similar procedure may be used to measure η by using a pairof sensors located diametrically opposite one another on the drogue 100.Each sensor may measure an angle η₁ and η₂ respectively, as shown inFIG. 19. The true angle η may be obtained by averaging these two angles.Still further, it is noted that while the Figures show that the anglesare being measured from a single reference point 2150, other embodimentscould measure angles from multiple reference points. By way of example,a first angle might be measured to a first reference point 2150, and asecond angle might be measured to a second reference point exactly 180degrees on the other side of the probe 2100. Thus, in such anembodiment, the position of the drogue 100 might be changes so thatthese angles become, for example, substantially equal to each other.Still further, it is noted that other embodiments may be practiced withmultiple sensors and/or multiple reference points.

In other embodiments of the present invention, the autonomous dockingsystem may be configured to measure a relative displacement utilizingCartesian coordinates. In yet other embodiments of the invention, anymeans that may be utilized to determine the relative locations of therefueling drogue 100 with respect to the refueling probe 2100 of areceiver aircraft 2000 may be utilized to practice the invention.

In the first embodiment of the invention, the autonomous docking systemmay be configured to regulate the location of the refueling drogue 100with respect to the refueling probe 2100 of the aircraft 2000 so thatthe just mentioned first and second angles are reduced. In someembodiments, the first and second angles are reduced to about zero orzero. In other embodiments of the invention, the position of the drogue100 is regulated so that the angles are such that they result in coaxialalignment of the probe and drogue based on the offsets of the points 700and the point 2150 from the drogue 100 centerline. Thus, a controlsystem may be utilized including a feedback system which may be ananalogue system and/or a digital system, where the autonomous dockingsystem determines that the refueling drogue 100 and the probe 2100 arealigned based on angle measurements of zero or substantially zero orother angle measurements. In some embodiments of the invention,circuitry that utilizes a feedback system and/or gain and/or errorsignals to generate control signals may be used to practice theinvention. By way of example, the first and second angles may beconverted to error signals, inputted into the circuit, and the circuitmay output a control signal to the active control system so that the“error” will be reduced, thus reducing the first and second angles tosubstantially zero. (In some embodiments, a similar system/same systemmay be used to implement the active control system.) Thus, theautonomous docking system may be in communication with the automaticcontrol system described above. Indeed, in some embodiments of thepresent invention, the automatic control system and the autonomousdocking system may be embodied in one system.

According to one embodiment of the invention, once the centerline of therefueling drogue 100 is coaxial or substantially coaxial with thecenterline of the refueling probe 2100, as discussed above, therefueling hose 800 connecting to the refueling drogue may be extended(“reeled out”) from the refueling aircraft 1000 a distance until therefueling drogue 100 captures the refueling probe 2100 of the receiveraircraft 2000. It is further noted that the canopy and/or parachute 114may provide additional resistance to the insertion of the probe 2100into the receptacle of the refueling drogue 100. That is, the extra dragresulting from the canopy and/or parachute 114 may allow the drogue 100to latch onto the probe 2100.

It will be noted that in some embodiments of the present invention, allof the components and/or some of the components making up the activecontrol system may be used to practice autonomous docking. Recognizingthat some embodiments of the invention implementing active controlutilize an angle(s) based on the axis 820 of the refueling drogue 800and or positions x, y, z of the of the drogue relative to the refuelingaircraft to regulate the location of the refueling drogue 100 and/ordetermine the location of the refueling drogue 100, autonomous dockingmay utilize this angle(s) to implement autonomous docking as well.However, in other embodiments of the invention, autonomous docking maybe performed without regard to the angle based on the axis 820 of thehose 800 and instead entirely be based on the angles between the drogue100 and the probe 2100 (e.g. λ, η). In yet other embodiments of theinvention, the combination of the angles may be used for autonomousdocking. By way of example, logic may be utilized to shift locationregulation of the drogue 100 from a location based on the angle of theaxis 820 of the refueling hose 800 to location regulation based onangle(s) between the drogue 100 and the probe 2100 to practiceautonomous docking.

In some embodiments of the present invention, the autonomous dockingsystem utilizes a sensor that can locate a point on the refueling probe,and thus measure the angles η and λ. In a first embodiment, thedirectional coordinates of radiation (which includes optical radiation)are used to determine the first and second angles. In a firstembodiment, the drogue 100 includes a radiation emitter 705. The firstembodiment of the invention, radiation (e.g., microwave and/or anoptical beam) is emitted from the radiation emitter 705 and directedtowards a radiation reflector on the refueling probe 2100 of thereceiver aircraft 2000. The autonomous docking system may also include aradiation receiver 710 optionally mounted on the drogue 100, thatreceives radiation reflected from this radiation reflector (or,alternatively, receives radiation generated from the receiver aircraft2000). The received radiation may be used to measure the anglesdiscussed above. In some embodiments, the radiation receiver 710 mayreceive optical radiation from the probe 2100. Indeed, in someembodiments of the present invention, the drogue 100 need not have aradiation emitter 705. That is, some embodiments of the presentinvention may be practiced where the receiver aircraft emits theradiation detected by radiation receiver 710. In some such embodiments,the receiver 710 may be considered as homing in on the radiation emittedby the receiver aircraft, just as one may home in on a homing beacon.

It is also noted that in some embodiments of the invention, a devicethat emits radiation that varies about the device may be located on thereceiver aircraft 2000, and in particular on the refueling probe 2100 ofthe aircraft 2000. The refueling drogue 100 may be configured with adevice that will detect the variations in the radiation/field, andcorrelate those variations to an angular displacement between the probe2100 and the drogue 100, thus enabling the autonomous docking system toalign the axis of the drogue 100 with the axis of the refueling probe2100 of the receiver aircraft 2000.

In the first embodiment of the present invention, the radiation could bean optical beam or a microwave beam. In the case of a microwave source,a simple transponder and/or a reflector, such as a corner reflectorlocated on the probe, may be used that retransmits energy toward thesource whenever it is energized by a microwave beam. The radiationreceiver on the drogue 100 may be used to determine the relative angleor angles between the refueling drogue 100 and the refueling probe 2100.In some embodiments of the present invention, there may be a pluralityof sensor configurations that could scan an area of about plus or minus45 degrees from the centerline 105 of the drogue 100 in each of the twoorthogonal directions.

The first embodiment of the invention may include a receiver that isadapted to receive an identification code from the receiver aircraft2000. In some embodiments of the present invention, the identificationcode is not required for angle measurement. The first embodiment of theinvention, the autonomous docking system may be configured to comparethis identification code to a code stored in a database to determine theidentity of the receiver aircraft 2000. In the first embodiment of theinvention, this could be a simple transponder or corner reflector thatretransmits energy to the source, wherein the retransmitted energycontains an identification code such that the signal is distinguishable.In some embodiments of the invention, the code may have information thatcan be utilized to determine the location and/or to adjust the offset ofthe basket.

It is noted that in some embodiments of the invention, when thecenterlines of the refueling drogue 100 and the centerline of therefueling probe 2100 are substantially coaxial, the relative lateralpositions of the drogue 100 and the probe 2100 may be controlled to, byway of example, about 6 inches and/or a few inches.

A number of sensor configurations may be used to transmit/receiveradiation according to the present invention. For example, a narrow beamlaser may transmits a beam to a mirror that may be rotated about atransverse axis thereby scanning a region. The reflected laser beamscans in the plane of incidence at an angle twice as large as thedeflection angle of the mirror along the same optical path. (It is notedthat sources other than a laser may be used.) The reflector structurethat may be located on the refueling probe may be a simple mirror cornerreflector. When illuminated by the source, the corner reflector may senda reflected signal back to the scanning mirror. An optical detectorlocated at the source (near the scanning mirror) may generate a narrowelectrical pulse when it receives this reflected signal. The angularposition of the mirror at the instant this reflected pulse is receivedmay yield a measurement at the relative angular position of the probe.

A relatively simple and inexpensive scanning microwave sensor can beimplemented using a technique including locating a ferrite cylinder inthe aperture of a section of rectangular waveguide. The ferrite materialis magnetically biased via a simple electromagnet, and the relativelynarrow microwave beam may be transmitted by the ferrite loaded waveguide(acting as an antenna). The angular deflection of this transmitted beammay vary proportionally (and maybe linearly) with the strength of thebiasing magnetic field (i.e. the deflection may vary in proportion tothe current through the electromagnet coil). The reflector in this casemay either be a microwave corner reflector or a suitable transponder,either of which is located on the probe structure.

Some embodiments of the present invention may be practiced toeffectively stabilize a refueling drogue subjected to an air stream at150 KEAS at a 5,000 ft pressure altitude by rotating the rotatable massat about 3,600 or a maximum of about 3,600 revolutions per minute, wherethe rotatable mass has a mass of about 20% of the total drogue mass, toobtain about a 4.3 to 1 reduction in the standard deviation of angulardeflection of the drogue, as compared to a refueling drogue without aspinning mass, while other embodiments may obtain about a 3-8 to 1reduction. Still other embodiments, when practiced in the just describedenvironment with an active control system according to the presentinvention, may be used to obtain an improvement of about 11.5 times inthe standard deviation of angular deflection, which may correspond to achange from about ±0.6 feet of displacement without spin to about ±0.05feet of displacement with spin.

While the above embodiments have been described in terms of a refuelingdrogue 100 with the rotating mass 200 and the air turbine 300, otherembodiments may be practiced. By way of example and not by limitation,an embodiment of the present invention may include a stabilization kitthat includes a spin stabilization pack 3000, as shown in FIG. 10, thatis configured to attach to a refueling drogue 4000 and/or a refuelinghose 800 that may “retrofit” an existing refueling drogue, such as byway of example and not by way of limitation, an MA-3 Drogue, to bepassively stabilized according to the present invention. Thestabilization pack 3000 might include the same or similar attachmentdevice 3100 that is used to attach a standard refueling drogue to arefueling hose 800. In some embodiments, the pack 3000 might include aflexible joint, which may be located between attachment device 3100 andthe rotating mass, allowing the rear portions of the pack (including therotating mass) to pivot, and thus allowing the drogue to pivot, while inother embodiments the pack might not include a joint. In someembodiments practiced on a drogue that has a pivot joint, the drogue maybe adapted so that the drogue will not pivot about that point, such as,by way of example, inserting a strap in a cavity around the joint,creating interference contact with the pivoting components, etc. Someembodiments of the pack 3000 may be practiced with any device that willpermit the pack to be attached to a refueling hose 800 of an aircraft.

An exemplary embodiment of a conventional refueling drogue 10 can beseen in FIG. 21. Here, a flexible joint 15 permits the body of thedrogue 10 to pivot. In some embodiments of the invention, this flexiblejoint may be replaced with a non-flexible joint. A pack 3000 may then beattached to component 20, thus causing the rotating mass of the pack3000 to be rigidly connected to the body of the refueling drogue 10. Asthe pack 3000 may have a flexible joint between the hose attachmentlocation of the pack 3000 and the rotating mass of the pack, which maybe similar to and/or the same as the flexible joint 15 shown in FIG. 21,the retrofitted drogue may be allowed to thus pivot with respect to thehose 800. This flexible joint can be used in the refueling drogue 100 aswell.

The pack 3000 may include a body 3200 enclosing the air turbine 350(radial turbine), having air inlet ports 120 and outlet ports 130. In afirst embodiment, the air turbine 350 may also serve as the rotatingmass.

Some embodiments of the present invention may have a brake that can stopand/or slow the rotation of the rotating mass 200 and/or the air turbine300. Some embodiments may utilize a friction brake, while otherembodiments may utilize a device to stop the flow of air past the airturbine, thus allowing the mass and/or air turbine to slow andeventually stop or at least rotate at a lower nominal value.

The pack 3000 may also include a refueling drogue attachment fitting3300 that is configured to receive a typical conventional refuelingdrogue 4000. In a first embodiment of the present invention, the pack3000 is configured to be rigidly attached to the refueling drogue 4000.In still further embodiments of the present invention, the pack 3000 isconfigured to attach to the refueling drogue 4000 in the same manner orin a similar manner as a conventional refueling hose 800 is currentlyattached to a conventional refueling drogue 4000. It is noted that thepack 3000 may be configured to also permit aviation fuel to travelthrough and/or around the pack 3000.

Still further, other embodiments of the present invention include kitsthat comprise devices that will enable conventional refueling drogue tobe retrofitted to be actively controlled and/or to perform an autonomousdocking mission according to the present invention. Such devices mightbe of similar kind to the pack 3000, except that the pack has featuressuch as control surfaces, sensors, etc., necessary to implement activecontrol and/or autonomous docking. In some embodiments of the presentinvention, a pack may have the passive stabilization system and/or theactive control system and/or the autonomous docking system in one pack,or at least the components that physically interface with the air stream(e.g., the vanes, the control surfaces, etc.) required to implementthose systems (the other components may be added directly to therefueling aircraft as long as there is a means to interface with theretrofit packs). Thus, any kit/pack that contains any or all of theabove elements of the active control and/or autonomous docking and/orpassive stabilization embodiments and/or will permit the implementationof the functions of active control, and/or autonomous docking and/orpassive stabilization, on an existing refueling drogue, may be utilizedto practice some embodiments of the invention

It is further noted that the present invention includes software,firmware and/or computers (including simple logic and/or error circuits)adapted to implement the above stabilization and/or control techniquesand/or docking techniques. Also, while some embodiments of the presentinvention may be practiced manually (such as, for example, use of anoperator to fly the drogue 100 to the receiver aircraft) otherembodiments may be practiced automatically. Thus, the present inventionincludes any device or system that may be configured or otherwise usedto implement the present invention in an automated manner.

It is noted that in other embodiments of the present invention, therefueling hose 800 might be passively stabilized by placing a rotatingmass on the refueling hose instead of or in addition to on the refuelingdrogue. In such embodiments, a spin stabilization pack for the refuelinghose similar to and/or the same as the pack 3000 might be used toretrofit existing refueling hoses to the spin stabilized configuration.

Some embodiments of the present invention may be practiced with anydevice or system that will enable a conventional refueling drogue and/orrefueling hose to be converted to a passively stabilized refuelingdrogue and/or refueling hose according to the present invention.

As noted above, some embodiments of the present invention may harnessthe rotational energy from the air turbine 300 to generate power. Suchgenerated power might be used to power lighting, control systems,recharging a component on the receiver aircraft, and/or communications.

Still further, the present invention may be practiced in combinationwith other techniques used in aerial refueling, such as varying theshape/deployment of a parachute-like canopy attached to the rear of thebasket of a refueling drogue. Still, other embodiments of the presentinvention may be practiced without varying the shape/deployment of aparachute-like canopy.

It is noted that the technique described above to passively stabilizethe refueling drogue may be applied on an aircraft wide basis. Byinstalling one or more spin stabilization units that may be rotated byutilizing air directed from outside the aircraft (while in otherembodiments a unit may be spun utilizing aircraft power and/or apre-liftoff spin up, relying on the inertia of the spinning mass tomaintain high enough RPMs). The rotating mass might be utilized topassively stabilize the aircraft and/or to offer limited control of theaircraft. Thus, the aircraft might be controlled without the need ofdrag inducing control surfaces such as, by way of example, slats andcontrol vanes. Such implementations might be applicable to rockets,missiles, helicopters and any form of aircraft. Also, it might beapplicable to sea vessels, such as submarines, torpedoes, ships, etc.The present invention may also apply to towed sea objects, for instancesonobuoys.

Typically, in airborne applications, it is the entire body of a rocket,missile, or similar structure that is made to spin to improve thatbody's stability during flight. Stability is achieved at the expense of(reduced) distance traveled (via increased drag, for example). Oneapplication concept would be to attach a spin-capable device orstructure to an otherwise non-rotating rocket or missile body to impartstability (as opposed to or in addition to adding vanes which spins theentire rocket). This device may improve the overall distance traveledduring flight since the entire body is not rotating, besides stabilizingthe body motion. The present invention may also be applicable to towedair vehicles, for instance drones.

In the general area of human physiology, there is an analogy between theinner ear and a 3-axis gyro. When combined with other sensoryobservations, the operation of the inner ear assists in establishingorientation (balance and stability). When the operation of the inner earis lost or damaged, an individual often loses the ability to walk viathe loss of balance. Some embodiments of the invention include an add-onspinning device that is of a miniaturized configuration and is adaptedto human use to augment stability and balance.

In the general area of sports equipment, an add-on spin device may be ofuse for arrows or other projectiles requiring stability for accuracyconsiderations. Possibly a ball (e.g., football) may benefit from spinadd-on. Also, toys may benefit from an added spin stabilizationstructure.

The following U.S. patents, the contents of which are incorporatedherein by reference in their entirety, may be utilized with the presentinvention: JUNKINS, et al. “Noncontact Position and OrientationMeasurement System and Method”, U.S. Pat. No. 6,266,142 B1, Jul. 24,2001; HARBURG, et al. “Self Regulating Pinwheel Kite Tail”, U.S. Pat.No. 5,183,224, Feb. 2, 1993; STEVENS, et al., “Autonomous Systems ForThe Aerial Refueling Or Decontamination Of Unmanned Airborne Vehicles”,U.S. Pat. No. 6,604,711 B1, Aug. 12, 2003; OLLAR, “Aerial Refueling PodAnd Constant Tension Line Apparatus”, U.S. Pat. No. 6,601,800 B2, Aug.5, 2003; RUZICKA, “Automated Director Light System for Aerial refuelingOperations” U.S. Pat. No. 5,904,729, May 18, 1999; AMBROSE, et al.“Telescoping Refueling Probe”, U.S. Pat. No. 6,598,830 B1, Jul. 29,2003; KIRKLAND, et al. “Passive Variable Speed Drogue”, U.S. Pat. No.6,588,465 B1, Jul. 8, 2003; BANDAK, “Paradrogue Assembly”, U.S. Pat. No.6,464,173 B1, Oct. 15, 2002; GREENHALGH, et al. “Air Refueling Drogue”,U.S. Pat. No. 6,375,123 B1, Apr. 23, 2002; MOUSKIS, et al. “DrogueAssembly For In-Flight Refueling”, U.S. Pat. No. 6,145,788, Nov. 14,2000; YOUNG, et al. “Drogue Assembly For In-Flight Refuelling”, U.S.Pat. No. 6,119,981, Sep. 19, 2000; WARD, “Hose And Drogue Boom RefuelingSystem, For Aircraft”, U.S. Pat. No. 5,573,206, Nov. 12, 1996; KIRKLAND,“Variable Speed Drogue”, U.S. Pat. No. 5,427,333, Jun. 27, 1995;KRISPIN, et al. “Controllable Hose-And-Drogue In-Flight RefuelingSystem”, U.S. Pat. No. 5,326,052, Jul. 5, 1994; ALDEN, et al. “AerialRefueling System”, U.S. Pat. No. 5,141,178, Aug. 25, 1992; EMERSON, etal. “Aerodynamic Controllably Vented Pressure Modulating Drogue”, U.S.Pat. No. 4,927,099, May 22, 1990; PATTERSON, “Aerodynamic Drag Device”,U.S. Pat. No. 2,998,949, Sep. 5, 1961; GORDON, et al. “Aerodynamic DragService”, U.S. Pat. No. 2,946,543, Jul. 26, 1960; PATTERSON, “ImprovedAerodynamic Drogue”, U.S. Pat. No. 2,823,881, Feb. 18, 1958; FINLAY,“Variable Area Drag Chute”, U.S. Pat. No. 2,761,636, Sep. 4, 1956;COBHAM, “Apparatus For Towing And Refueling Aircraft In Flight”, U.S.Pat. No. 2,692,103, Oct. 19, 1954; WILLIAMS, et al. “Aircraft FlightRefueling Apparatus”, U.S. Pat. No. 2,596,455, May 13, 1952; and STEELE,“Means for Fueling Aircraft in Flight”, U.S. Pat. No. 2,582,609, Jan.15, 1952.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the present invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention accordingly is to be defined as set forth inthe appended claims.

1. A refueling drogue comprising: a refueling drogue; and an activecontrol system.
 2. The refueling drogue of claim 1, wherein the activecontrol system is adapted to regulate the vertical and horizontalposition of the drogue to maintain a substantially fixed orientationrelative to a refueling aircraft.
 3. The refueling drogue of claim 2,wherein the active control system is adapted to regulate the verticaland horizontal position of the drogue to maintain a substantially fixedorientation relative to a refueling aircraft when the refueling aircraftis flying at a substantially constant altitude, airspeed and heading. 4.The refueling drogue of claim 1, wherein the active control systemcomprises a plurality of control surfaces located on the refuelingdrogue.
 5. The refueling drogue of claim 4, wherein the plurality ofcontrol surfaces are located on a refueling drogue hose connector. 6.The refueling drogue of claim 1, wherein the active control systemcomprises two pairs of control surfaces orthogonal to one another. 7.The refueling drogue of claim 6, wherein the active control system isadapted to actively regulate the location of the refueling drogue atsubstantially any rotation angle of the control surfaces from at leastone of a horizontal plane and a vertical plane.
 8. The refueling drogueof claim 7, further comprising a sensor adapted to measure the rotationangle γ.
 9. The refueling drogue of claim 1, wherein the refuelingdrogue is adapted to be connected to a refueling hose, and wherein theactive control system further comprises a control system adapted toregulate an angle θ and an angle ψ of an axis through the center of therefueling hose at the location where the refueling hose connects to therefueling drogue.
 10. The refueling drogue of claim 9, furthercomprising a refueling hose connector rigidly connected to the refuelinghose, wherein at least a portion of the refueling hose connector isadapted to move relative to a main body of the refueling drogue, andwherein the angle θ and the angle ψ of the axis through the center ofthe refueling hose is regulated by regulating angles of the refuelinghose connector.
 11. The refueling drogue of claim 9, wherein the controlsystem is adapted to substantially maintain the angle θ and the angle ψof the axis through the center of the refueling hose at respectivereference angles.
 12. The refueling drogue of claim 11, wherein a yawangle of the axis of the refueling drogue is measured in a horizontalplane and is substantially zero degrees from a direction of the airstream, and wherein a pitch angle of the axis of the refueling drogue ismeasured in a vertical plane and is a non-zero angle from a referenceplane corresponding to the horizontal plane.
 13. The refueling drogue ofclaim 1, further comprising: a rotatable mass; wherein the rotatablemass is adapted to effectively stabilize the refueling drogue via agyroscopic effect of the rotating mass on the refueling drogue when therefueling drogue is placed in an airstream.
 14. The refueling drogue ofclaim 1, wherein the active control system comprises: a sensor adaptedto measure a varying angle between an axis through the center of therefueling hose at a location where the refueling hose is connected tothe refueling drogue and a direction of the air stream.
 15. Therefueling drogue of claim 1, further comprising: a first sensor adaptedto measure a first varying angle between an axis through the center ofthe refueling hose and a direction of the air stream; and a secondsensor adapted to measure a second separate varying angle between anaxis through the center of the refueling hose and the direction of theair stream; wherein the active control system is adapted to regulate thelocation of the refueling drogue based on the measured first varyingangle and the measured second varying angle.
 16. The refueling drogue ofclaim 15, wherein the drogue is adapted to permit the first sensor andthe second sensor to rotate relative to the horizontal plane and thevertical plane.
 17. The refueling drogue of claim 15, wherein the firstvarying angle lies on a plane that is substantially orthogonal to aplane on which the second varying angle lies.
 18. The refueling drogueof claim 15, wherein the first varying angle lies on a plane that is notsubstantially orthogonal to a plane on which the second varying anglelies.
 19. The refueling drogue of claim 17, further comprising a pair ofcontrol surfaces orthogonal to another pair of control surfaces, whereinthe plane on which the first varying angle lies is on a plane through anaxis of symmetry of the refueling drogue and orthogonal to a plane onwhich one of the pairs of control surfaces lies.
 20. The refuelingdrogue of claim 17, further comprising a first pair of control surfacesorthogonal to a second pair of control surfaces, wherein the plane onwhich the first varying angle lies is on a plane through the first pairof control surfaces and wherein the plane on which the second varyingangle lies is on a plane through the second pair of control surfaces.21. The refueling drogue of claim 15, wherein at least one of the firstsensor and the second sensor includes a rotary vane adapted to pivotabout a vane axis and a sensor adapted to output a signal indicative ofthe angle of pivot about the vane axis.
 22. The refueling drogue ofclaim 15, wherein at least one of the first and second sensors islocated substantially at a refueling hose-refueling drogue pivot point.23. The refueling drogue of claim 1, wherein the active control systemis adapted to reduce displacement of the refueling drogue to about 12inches or less when exposed to moderate turbulence.
 24. The refuelingdrogue of claim 2, wherein the active control system is adapted toreduce displacement of the refueling drogue to about 6 inches or lesswhen exposed to moderate turbulence.
 25. The refueling drogue of claim1, wherein the active control system is adapted to reduce displacementof the refueling drogue to a few inches or less when exposed to moderateturbulence.
 26. The refueling drogue of claim 1, wherein the refuelingdrogue is connected to a refueling hose, wherein the active controlsystem is adapted to compute a pitch angle θ′ and a yaw angle ψ′ of anaxis through the center of the refueling hose at a location where therefueling hose connects to the refueling drogue.
 27. The refuelingdrogue of claim 26, further comprising a computer adapted to calculateat least one of a displacement and a position of the refueling droguebased on the measured pitch angle and the yaw angle of the axis throughthe center of the refueling hose.
 28. The refueling drogue of claim 26,further comprising a computer adapted to calculate at least one of adisplacement and a position of the refueling drogue based on themeasured pitch angle and the yaw angle of the axis through the center ofthe refueling hose and a proportionality constant.
 29. The refuelingdrogue of claim 28, wherein the displacement and the position of therefueling drogue is calculated utilizing an algorithm having afoundation in the equations:y=f(θ′), andz=g(ψ′), where y=a distance in the plane in which the angle θ lies; z=adistance in the plane in which the angle ψ lies, θ′=the pitch angle ofthe refueling hose, and ψ′=the yaw angle of the refueling hose, and fand g are functions that describe the relation between y and θ′ and zand ψ′.
 30. The refueling drogue of claim 1, further comprising anautonomous docking system.
 31. The refueling drogue of claim 13, furthercomprising an autonomous docking system.
 32. The refueling drogue ofclaim 30, wherein the autonomous docking system is adapted to vary theposition of the refueling drogue so that a centerline of the refuelingdrogue remains substantially coaxial with a centerline of a refuelingprobe of a receiver aircraft that is not yet in contact with therefueling drogue.
 33. The refueling drogue of claim 32, wherein theautonomous docking system comprises a sensor, and wherein the autonomousdocking system is adapted to vary the position of the refueling droguebased on information received by the sensor indicative of the positionof an end of the refueling probe of the receiver aircraft.
 34. Therefueling drogue of claim 32, wherein the autonomous docking system isadapted to measure an angle η and an angle λ between the refuelingdrogue and a point on the refueling probe of the receiver aircraft, andwherein the autonomous docking system is adapted to vary the position ofthe refueling drogue based on the measurements of these angles.
 35. Therefueling drogue of claim 34, wherein the autonomous docking system isadapted to measure a plurality of angles η and average the plurality ofangles η and an a plurality of angles λ and average the plurality ofangles λ between the refueling drogue and a point on the refueling probeof the receiver aircraft, and wherein the autonomous docking system isadapted to vary the position of the refueling drogue based on theaverages of these angles.
 36. The refueling drogue of claim 34, whereinthe autonomous docking system is adapted to position the refuelingdrogue so that the average of the of the measured plurality of angles ηand average the plurality of measured angles η are substantially reducedto zero.
 37. The refueling drogue of claim 32, wherein the autonomousdocking system comprises a radiation receiver, and wherein theautonomous docking system is adapted to vary the position of therefueling drogue based on received radiation indicative of the positionof an end of the refueling probe of the receiver aircraft.
 38. Therefueling drogue of claim 37, further comprising a radiation emitterlocated on the refueling drogue.
 39. The refueling drogue of claim 37,wherein the receiver is adapted to receive radiation emitted from areceiver aircraft.
 40. The refueling drogue of claim 37, wherein thereceiver is adapted to receive at least one of a microwave beam and anoptical beam.
 41. The refueling drogue of claim 37, wherein the receiveris adapted to receive an identification code, and wherein the autonomousdocking system is configured to compare the identification code to acode in a database.
 42. The refueling drogue of claim 37, wherein thereceiver is adapted to sense at least one of a varying signal and avarying field, wherein the at least one of a varying signal and avarying field varies based on the location of the receiver aircraft. 43.The refueling drogue of claim 30, wherein the autonomous docking systemis adapted to automatically maneuver the refueling drogue to therefueling probe of the receiver aircraft.
 44. The refueling drogue ofclaim 30, wherein the autonomous docking system is adapted to measure anangle between the refueling drogue and the refueling probe of thereceiver aircraft.
 45. The refueling drogue of claim 30, wherein theautonomous docking system is adapted to measure a first angle betweenthe refueling drogue and the refueling probe of the receiver aircraftmeasured on a first plane and to measure a second angle between therefueling drogue and the refueling probe of the receiver aircraftmeasured on a second plane.
 46. The refueling drogue of claim 45 whereinthe autonomous docking system is adapted to regulate the location of therefueling drogue relative to the refueling probe of the receiveraircraft so that the first and second angles are reduced.
 47. Therefueling drogue of claim 46, wherein the autonomous docking system isadapted to adjust the location of the refueling drogue relative to therefueling probe of the receiver aircraft so that the first and secondangles are reduced to substantially zero degrees.
 48. The refuelingdrogue of claim 47, further comprising a control circuit utilizing anerror signal input to regulate the location of the refueling drogue sothat the first and second angles are reduced to substantially zerodegrees, wherein the circuit is adapted to convert the first and secondangles to error signals.
 49. The refueling drogue of claim 1, furthercomprising an autonomous docking system, wherein the autonomous dockingsystem is in communication with the control system to vary the positionof the refueling drogue so that a centerline of the refueling drogueremains substantially coaxial with a centerline of a refueling probe ofa receiver aircraft that is not yet in contact with the refuelingdrogue.
 50. The refueling drogue of claim 1, further comprising anautonomous docking system, wherein the autonomous docking system is incommunication with the control system and adapted to maneuver therefueling drogue to a refueling probe of a receiver aircraft.
 51. Therefueling drogue of claim 1, wherein the active control system comprisesan autonomous docking system, adapted to maneuver the refueling drogueto a refueling probe of a receiver aircraft.